Silicon dioxide

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 February 2017 to 16 Febraury 2017 (first test); 26 June 2017 to 29 June 2017 (second test)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

2011

Deviations:

yes

Remarks:

Temperature during the 2nd experiment was not within the range specified in the guideline (21-24 °C, controlled to +/-2°C). Since normal growth in the blank control was observed, this deviation was considered to have no effect on the results of the study

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

December 2015

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

First test: A saturated solution was prepared using plastic vessels. To the nominal load of 50 g/L, the corresponding amount of algal medium was added. After homogenisation by using an ultrasonic bath for 1 min and shaking vigorously for 72 hours, undissolved test item was removed by centrifugation at 4500 rpm for 10 minutes followed by filtration using a nylon filter 0.45 µm. The visually clear liquid was used for the OECD 201 test. The lower treatments were prepared by diluting this saturated solution with algal medium.

Second test: A saturated solution was prepared using plastic vessels. To the nominal load of 50 g/L, the corresponding amount of demineralised water was added. After homogenisation by using an ultrasonic bath for 1 min and shaking vigorously for 72 hours, a small sample was taken, filtrated using a nylon filter (0.45 µm), and the Si content was measured using ICP-OES.
From the rest of the stock solution undissolved test item was removed by centrifugation at 4500 rpm for 10 minutes followed by filtration using a nylon filter 0.45 µm.
Again a small sample was taken for determination of its Si content with ICP-OES and for determination of undissolved particles using a Tyndall device. The necessary amounts of stock solutions for preparation of algal medium were added. The stock solution was visually checked for any precipitation and for undissolved particles using a laser and the Tyndall device. As no particles were observable, a sample was taken for Si measurement.
The lower treatments were prepared by diluting this saturated solution with algal medium.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

The culture of Desmodesmus subspicatus was obtained in January 2016 from MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen, Germany). The algae were kept as stock culture on solid agar at 2 - 8 °C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

no

Hardness:

Not specified

Test temperature:

first test: 21.8 - 22.8 °C;
second test: 20.8 - 24.6 °C.

pH:

First test:
at 0 hrs 7.7, 7.7, 7.7, 7.6, 7.3, 6.5 for blankk control, 0.5, 1.5, 5, 16, and 50 mg/L
at 72 hrs 8.2, .8.3, 8.0, 7.8, 7.7, 6.8 for blankk control, 0.5, 1.5, 5, 16, and 50 mg/L
Second test:
at 0 hrs 8.2, 8.3, 8.3, 8.2, 8.0, 7.5 for blankk control, 0.5, 1.5, 5, 16, and 50 mg/L
at 72 hrs 8.5, 8.7, 8.4, 8.6, 8.8, 8.6 for blankk control, 0.5, 1.5, 5, 16, and 50 mg/L

Dissolved oxygen:

Not specified

Salinity:

Not applicable

Conductivity:

not specified

Nominal and measured concentrations:

nominal test concentrations of 0, 0.5, 1.5, 5, 16, 50 g/L were used in both experiments

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 173.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 173.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

other: yield

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

173.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

173.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

other: yield

Details on results:

The Si content of the test item in the test solutions was determined by ICP-OES at the start and at the end of the test. In the first test, the measured concentrations in the highest concentrated treatment group were 129.60 mg/L (as SiO2) at the beginning and 138.75 mg/L (as SiO2) at the end of the study. In the second test, the deviation of the measured concentrations was greater than 20 % of the nominal concentration; therefore, the results were reported based on the geometric means of the measured concentrations.

Results with reference substance (positive control):

The 72h-EC50s of potassium dichromate (K2Cr2O7, CAS No. 7778-50-9) were determined in a separate reference test. The results were within the normal ranges for this reference item (EC50 growth rate 0.73 - 1.10 mg/L, EC50 yield 0.21 – 0.66 mg/L).

Inhibition of algal growth was scattered in all treatments of the first experiment; statistically significant inhibition of algal growth was observed in all concentration except for a loading dose of 16 g/L. The inhibition values did not follow a dose-response relationship. The reasons for this anomaly could not be determined and the results of this experiment were not used for the determination of the biological results.

Validity criteria fulfilled:

yes

Conclusions:

The substance exhibits a low acute toxicity towards algae (EC50 growht rate is > 173 mg/L, EC50 for yield is > 173 mg/L); the 72-hr NOECs for growth rate, AUC and Yield are all at > 173 mg/L.

Executive summary:

The effect of the test item on algae was assessed in a GLP and guideline study (OECD testing guideline 201) using the green alga Desmodesmus subspicatus, over an exposure period of 72 hours. The NOEC (growth rate, yield) was 173 mg/L (dissolved fraction, the highest tested concentration), with the EC50 values for both growth rate and for yield at > 173 mg/L.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Remarks:

high-nutrient MBL medium was used

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Deviations:

yes

Remarks:

high-nutrient MBL medium was used as described by Nichols, 1973

GLP compliance:

not specified

Remarks:

Study was performed in the laboratory of an internationally highly reputated researcher

Specific details on test material used for the study:

The test materials were provided by Nouryon (Sweden). The studies were performed using biocide-free silicas which were sampled directly at the Levasil production line, prior to the biocides being added to the final product.
The selected Levasil particles were either spherical uncoated, Na-stabilised particles (17–88 nm mean particle diameter), or surface modified (alumina-, silane-modified)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Particle sizes of dispersions were analyzed at the highest tested concentration and at 158 mg/L in algae medium without organisms

Test organisms (species):

Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)

Details on test organisms:

Raphidocelis subcapitata (strain 61.81 from Experimental Phycology and Culture Collection of Algae (EPSAG), Göttingen, Germany), formerly known as Selenastrum capricornutum and Pseudokirchneriella subcapitata

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22.8 ± 0.45 °C

Nominal and measured concentrations:

Five test concentrations in the range 5–500 mg/L (three replicates and a minimum of six untreated controls)

Details on test conditions:

The assay was performed in 70 mL Nunc™ sterile flasks (containing a total test suspension of 10 mL), which were incubated in a 16:8 h light: dark cycle (7690 ± 160 lx). Algal cell numbers were measured after 72 h exposure in a flow cytometer (CyFlow® Cube 8, Partec Nordic AB) with an autoloading station (CyFlow® Robby 8, Partec Nordic AB) in order to calculate growth inhibition based on the specific growth rate.

Reference substance (positive control):

yes

Remarks:

Paraquat (1–50 μmol/L)

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 500 mg/L

Nominal / measured:

nominal

Remarks on result:

other: in high-nutrient MBL medium

Remarks:

18 nm-silanized, 20nm-aluminized, 21nm, 30nm, 66nm, 88nm particles

Key result

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

295 mg/L

Nominal / measured:

nominal

Remarks on result:

other: in high-nutrient MBL medium

Remarks:

17nm particles

Details on results:

With the exception of the 17 nm particle which resulted in a slight toxic effect to algae (EC20: 295 mg/L), no toxicity was observed.

Reported statistics and error estimates:

Concentration response curve modelling and calculation of ECx values were performed in R (version R-3.3.1). Three different models were tested for “best-fit” including two different two-parameter Weibull functions and one two-parameter log-logistic function. The “best-fit” was selected based on analysis of the residues and visual inspection of the fit. Inhibition for algae was calculated using a trimmed mean of the controls, n = 4,

Validity criteria fulfilled:

not specified

Conclusions:

The negatively charged colloidal silica nanoparticles were not toxic to Pseudokirchneriella subcapitata (EC50 > 500 mg/L).

Executive summary:

Seven grades of colloidal silica were tested for their toxicity to the green algae Pseudokirchneriella subcapitata in a study performed in accordance with OECD test guideline 201, but using high-nutrient algal medium instead of standard medium. The grades tested were sampled directly from the production line before the addition of biocides. No toxicity was observed with EC50 values higher than 500 mg/L for 6 of the 7 tested grades and an EC20 vaue for Na-stabilised uncoated 17nm particles of 295 mg/L. The authors of this study concluded that "the comparatively high toxicity of silica particles observed by Van Hoecke et al. is therefore likely caused at least partly by added biocide."

Reference 3

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

2009

Deviations:

yes

Remarks:

64 mg instead of 80 mg FeCl3*6H2O/L in stock solution to prepare culture medium

GLP compliance:

no

Specific details on test material used for the study:

The eluate was tested

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

no

Hardness:

Not specified

Test temperature:

25 - 26 °C

pH:

7.5

Dissolved oxygen:

Not specified

Salinity:

Not applicable

Conductivity:

not specified

Nominal and measured concentrations:

7 nominal test concentrations up to 1000 mg/L

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Details on results:

The Test was performed with the eluate; the colloidal particles were removed by using a ultra centrifuge.

Results with reference substance (positive control):

Potassium dichromate was used as the reference item. Exposure conditions and data evaluation for the positive control were similar to those in the definitive test.
The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

Validity criteria fulfilled:

yes

Conclusions:

As regards the eluate, NOEC and EC50 values for growth were all above 1000 mg/L, indicating that the contained biocide is tightly bound to the silica matrix and not eluated.

Executive summary:

The effect of the eluate of the test item on algae was assessed in a non-GLP study using the green alga Desmodesmus subspicatus, over an exposure period of 72 hours. The NOEC (growth rate, yield) was above 1000 mg/L. EC50 values for growth and yield were at >1000 mg/L. The results indicate that the biocide is tightly bound in the silica matrix and not eluated.

Reference 4

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

other information

Study period:

26 March 2012 to 29 March 2012 (in-life phase)

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

2009

Deviations:

yes

Remarks:

64 mg instead of 80 mg FeCl3*6H2O/L in stock solution to prepare culture medium

GLP compliance:

no

Specific details on test material used for the study:

The eluate was tested

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

no

Hardness:

Not specified

Test temperature:

25 - 26 °C

pH:

7.5

Dissolved oxygen:

Not specified

Salinity:

Not applicable

Conductivity:

not specified

Nominal and measured concentrations:

7 nominal test concentrations up to 1000 mg/L

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Results with reference substance (positive control):

Potassium dichromate was used as the reference item. Exposure conditions and data evaluation for the positive control were similar to those in the definitive test.
The results from the positive control with potassium dichromate were within the expected range for this reference item.

Validity criteria fulfilled:

yes

Conclusions:

As regards the eluate of the test material, 72-h NOEC and EC50 values for growth and yield were all above 1000 mg/L

Executive summary:

The effect of the test item (eluate) on algae was assessed in a non-GLP study using the green alga Desmodesmus subspicatus, over an exposure period of 72 hours. The NOEC (growth rate, yield) was above 1000 mg/L. EC50 values for growth and yield were at >1000 mg/L.

Reference 5

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

other information

Study period:

24 October 2011 to 23 December 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

2009

Deviations:

yes

Remarks:

64 mg instead of 80 mg FeCl3*6H2O/L in stock solution to prepare culture medium

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Si content 18.7%

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

A stock solution containing 1250 mg/L test item in deionised water was prepared. From this stock solution, the concentrations to be tested were prepared by diluting with deonised water.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

no

Hardness:

Not specified

Test temperature:

23 - 24 °C

Dissolved oxygen:

Not specified

Salinity:

Not applicable

Conductivity:

not specified

Nominal and measured concentrations:

nominal test concentrations of 10, 22, 46, 100, 220, 460 and 1000 mg/L were used

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: extrapolated value

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

15 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

< 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

< 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield

Details on results:

The Si content of the test item in the test solutions was determined by AAS at the start and at the end of the test. The recoveries after 72 h were in the range between 96 and 110%, and between 97 and 117% of the nominal concentrations. The reporting of the results is therefore based on the nominal concentrations.

Results with reference substance (positive control):

Potassium dichromate was used as the reference item. Exposure conditions and data evaluation for the positive control were similar to those in the definitive test and resulted in the following values:
ErC50 (0 to 72 hour) : 1.2 mg/L; 95% confidence limits 1.1 to 1.4 mg/L
EyC50 (0 to 72 hour) : 0.48 mg/L; 95% confidence limits 0.43 to 0.53 mg/L
No Observed Effect Concentration based on growth rate: 0.25 mg/L
Lowest Observed Effect Concentration based on growth rate: 0.4 mg/L
The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

Validity criteria fulfilled:

yes

Conclusions:

EC50 values for growth were 66 mg/L (extrapolated) and for yield 15 mg/L; the 72-hr NOECs for growth rate, AUC and Yield are all below 10 mg/L, the lowest tested concentration.

Executive summary:

The effect of the test item on algae was assessed in a GLP and guideline study (OECD testing guideline 201) using the green alga Desmodesmus subspicatus, over an exposure period of 72 hours. The NOEC (growth rate, yield) was below the lowest tested concentration of 10 mg/L (LOEC). EC50 values for growth were at 66 mg/L (extrapolated) and for yield at 15 mg/L.

Reference 6

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

other information

Study period:

06 November 2012 to 09 November 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

2011

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

2009

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Si content 11.7%

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

A stock solution containing 125 mg/L was prepared in dilution water. The test solutions were prepared by diluting with dilution water.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

no

Hardness:

Not specified

Test temperature:

23 - 24 °C

pH:

at t=0hrs:
0 mg/L: 7.8, 4.6 mg/L: 7.9, 10 mg/L: 8.0, 22 mg/L: 8.0, 46mg/L: 8.0, 100 mg/L: 8.1
at t=72hrs:
0 mg/L: 7.7, 4.6 mg/L: 7.7, 10 mg/L: 7.8, 22 mg/L: 7.7, 46mg/L: 7.7, 100 mg/L: 7.6

Dissolved oxygen:

Not specified

Salinity:

Not applicable

Conductivity:

not specified

Nominal and measured concentrations:

nominal test concentrations of 4.6, 10, 22, 46, 100 mg/L were used in the definitive test

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 59 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

39 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: yield

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: yield

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

11 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

11 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: yield

Details on results:

The Si content of the test item in the test solutions was determined by AAS at the start and at the end of the test. The measured concentrations were between 41 and 56% of the nominal concentrations at the start, and between 38 and 61% at the end of the test, which was attributed to the observed precipitation of the test item in the test medium. All results were therefore based on the geometric mean of the measured concentrations.

Results with reference substance (positive control):

Potassium dichromate was used as the reference item. Exposure conditions and data evaluation for the positive control were similar to those in the definitive test and resulted in the following values:
ErC50 (0 to 72 hour) : 1.1 mg/L; 95% confidence limits 0.86 to 1.7 mg/L
EyC50 (0 to 72 hour) : 0.29 mg/L; 95% confidence limits 0.21 to 0.38 mg/L
No Observed Effect Concentration based on growth rate: 0.16 mg/L
Lowest Observed Effect Concentration based on growth rate: 0.25 mg/L
The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

Validity criteria fulfilled:

yes

Conclusions:

The substance exhibits a low acute toxicity towards algae (EC50 growth rate is > 59 mg/L, EC50 for yield is 39 mg/L); the 72-hr NOECs for growth rate, AUC and Yield are all at 4.0 mg/L with the LOEC at 11 mg/L.

Executive summary:

The effect of the test item on algae was assessed in a GLP and guideline study (OECD testing guideline 201) using the green alga Desmodesmus subspicatus, over an exposure period of 72 hours. The NOEC (growth rate, yield) was 4.0 mg/L, with the LOEC (growth rate, yield) at 11 mg/L. EC50 values for growth were at >59 mg/L and for yield at 39 mg/L.

Reference 7

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

other information

Study period:

17 October 2011 to 20 October 2011

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

2009

Deviations:

yes

Remarks:

64 mg instead of 80 mg FeCl3*6H2O/L in stock solution to prepare culture medium

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

26 nm, Si content in test item: 14.022 %

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

A stock solution containing 1250 mg/L test item in deionised water was prepared. From this stock solution, the concentrations to be tested were prepared by diluting with deonised water.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

no

Hardness:

Not specified

Test temperature:

26 - 27 °C

Dissolved oxygen:

Not specified

Salinity:

Not applicable

Conductivity:

not specified

Nominal and measured concentrations:

nominal test concentrations of 10, 22, 46, 100, 220, 460 and 1000 mg/L were used

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: extrapolated value

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

45 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

22 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

22 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

46 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

46 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield

Details on results:

The Si content of the test item in the test solutions was determined by AAS at the start and at the end of the test. The recoveries after 72 h were in the range between 86 and 107%, and between 93 and 105% of the nominal concentrations. The reporting of the results is therefore based on the nominal concentrations.

Results with reference substance (positive control):

Potassium dichromate was used as the reference item. Exposure conditions and data evaluation for the positive control were similar to those in the definitive test and resulted in the following values:
ErC50 (0 to 72 hour) : 1.20 mg/L; 95% confidence limits 1.1 to 1.4 mg/L
EyC50 (0 to 72 hour) : 0.48 mg/L; 95% confidence limits 0.43 to 0.53 mg/L
No Observed Effect Concentration based on growth rate: 0.25 mg/L
Lowest Observed Effect Concentration based on growth rate: 0.4 mg/L
The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

Validity criteria fulfilled:

yes

Conclusions:

EC50 values for growth were above 1000 mg/L and for yield 45 mg/L; the 72-hr NOECs for growth rate, AUC and Yield were all at 22 mg/L (LOECs all at 46 mg/L).

Executive summary:

The effect of the test item on algae was assessed in a GLP and guideline study (OECD testing guideline 201) using the green alga Desmodesmus subspicatus, over an exposure period of 72 hours. The NOEC (growth rate, yield) was at 22 mg/L (LOEC 46 mg/L). EC50 values for growth were at >1000 mg/L and for yield at 45 mg/L.

Reference 8

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

other information

Study period:

30 July 2012 to 02 August 2012

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

non-GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

2009

Deviations:

yes

Remarks:

64 mg instead of 80 mg FeCl3*6H2O/L in stock solution to prepare culture medium

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Si content 18.7%

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

A stock solution containing 125 mg/L test item in deionised water was prepared. From this stock solution, the concentrations to be tested were prepared by diluting with deonised water.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

no

Hardness:

Not specified

Test temperature:

25 °C

Dissolved oxygen:

Not specified

Salinity:

Not applicable

Conductivity:

not specified

Nominal and measured concentrations:

nominal test concentrations of 10, 18, 32, 56 and 100 mg/L were used; pre-test screening with 1, 10, 100 mg/L

Details on test conditions:

vessels: 50 mL glass flasks; six replicates for controls, 3 replicates for treatments

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

76 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

22 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: Yield

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

18 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

18 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: yield

Details on results:

The Si content of the test item in the test solutions was determined by AAS at the start and at the end of the test. The recoveries after 72 h were in the range between 101 and 113%, and between 88 and 110% of the nominal concentrations. The reporting of the results is based on the mean of the measured concentrations.

Results with reference substance (positive control):

Potassium dichromate was used as the reference item. Exposure conditions and data evaluation for the positive control were similar to those in the definitive test and resulted in the following values:
ErC50 (0 to 72 hour) : 1.4 mg/L; 95% confidence limits >1.1 mg/L
EyC50 (0 to 72 hour) : 0.38 mg/L; 95% confidence limits 0.30 to 0.47 mg/L
No Observed Effect Concentration based on growth rate: 0.25 mg/L
Lowest Observed Effect Concentration based on growth rate: 0.4 mg/L
The results from the positive control with potassium dichromate were within the normal ranges for this reference item.

Validity criteria fulfilled:

yes

Conclusions:

EC50 values for growth were 66 mg/L (extrapolated) and for yield 15 mg/L; the 72-hr NOECs for growth rate, AUC and Yield are all below 10 mg/L, the lowest tested concentration.

Executive summary:

The effect of the test item on algae was assessed in a GLP and guideline study (OECD testing guideline 201) using the green alga Desmodesmus subspicatus, over an exposure period of 72 hours. The NOEC (growth rate, yield) was below the lowest tested concentration of 10 mg/L (LOEC). EC50 values for growth were at 66 mg/L (extrapolated) and for yield at 15 mg/L.

Description of key information

For the assessment of the aquatic toxicity to algae and cyanobacteria of non-surface treated SAS, the database compiles 8 studies from 1999 to 2019. None of 7 OECD 201 tests performed under GLP environment showed an effect of the dissolved fraction on algal toxicity. The 72h-NOEC obtained were all above 100 mg/L and 72h-EC50 > 100 mg/L.

Special attention

Importantly, Results from guideline studies performed with some colloidal SAS products were not suitable for assessing algal toxicity of colloidal SAS per se, because some tested materials contained biocidal active substances. In addition, effects might also be related to direct interactions of particles (biocides are typically adsorbed on the particles surface)with the algae cell walls and/or with constituents of the culture medium via adsorption on the particle surface (nutrient elements such as Magnesium, Calcium), since the dissolved fractions do not show algal toxicity. Similar results were also obtained in published studies with biocide-containing colloidal SAS products (van Hoecke et al. 2008). A recently published study shows that pure colloidal SAS materials, i.e. those without added biocide, do not cause toxicity to algae in nutrient- enriched exposure media (Book et al. 2019). The presence of a biocide in a product containing colloidal SAS should therefore not be considered relevance for the classification of colloidal SAS, this hazard being taken into account by the contribution of the biocide itself.

References:

Book F, Ekvall MT, Persson M, et al. (2019) Ecotoxicity screening of seven different types of commercial silica nanoparticles using cellular and organismic assays: Importance of surface and size. NanoImpact 13:100-111 doi:https://doi.org/10.1016/j.impact.2019.01.001

Van Hoecke K, De Schamphelaere KA, Van der Meeren P, Lucas S, Janssen CR (2008) Ecotoxicity of silica nanoparticles to the green alga Pseudokirchneriella subcapitata: importance of surface area.Environmental toxicology and chemistry / SETAC 27(9):1948-57